A pilot, open study to assess efficacy and safety of ON-01910 (rigosertib) in patients with recessive dystrophic epidermolysis bullosa associated locally advanced/metastatic squamous cell carcinoma.
Authors: Lauren Banner, Linda Hosler, Matthew Parris, Mark Stephen Gelder, Martin Laimer, Johann Bauer, Andrew South, Neda Nikbakht
Journal: Journal of Clinical Oncology (2023)

TPS9604 Background: Recessive Dystrophic Epidermolysis Bullosa (RDEB) is an extremely rare, severe blistering disease driven by mutations in collagen seven (COL7A1). Besides the skin and mucosal blistering, this genodermatosis is also characterized by aggressive cutaneous squamous cell carcinomas (cSCCs) arising from patients’ chronic wounds. The cumulative risk of death from these cSCCs is 70% by age 45. There are limited effective treatment options for advanced (unresectable/metastatic) RDEB-associated cSCCs. While the standard of care for any advanced cSCC is immune checkpoint inhibitors, only half of the treated patients had responses in clinical trials. Their use for RDEB-associated SCCs been limited to case reports, and our own experience has not been positive. Conventional chemotherapy in RDEB-associated cSCC is another proposed treatment strategy, however, case reports demonstrated limited response rates without lasting effects. Currently it is recommended palliatively, although there are concerns about adverse effects. Other existing options are tyrosine kinase inhibitors, resulting in mixed responses to treatment for advanced cSCCs of any type, and epidermal growth factor receptor inhibitors, demonstrating limited effectiveness in a small number of case reports on RDEB-associated cSCCs. More effective therapeutic modalities for advanced/metastatic RDEB-associated cSCCs are needed. We previously demonstrated that RDEB SCC keratinocytes are specifically affected by polo-like kinase-1 (PLK-1) siRNA. Eight PLK-1 inhibitors were screened for cytotoxicity. Of the 8 candidates, ON-01910 was superior as it demonstrated the largest therapeutic window for distinguishing between tumor versus normal cells. The ON-01910 clinical trial is in progress in patients with RDEB with advanced/metastatic cSCCs. Methods: ON-01910 is being evaluated in both oral and intravenous formulations in an open-label, non-randomized phase 2 study in RDEB patients with advanced, treatment resistant cSCC. The trial explores the anti-tumor activity of ON-01910 and evaluates its safety and tolerability. Secondary objectives are to assess the impact on quality of life and to perform biomarker analysis on patient tissue. This study began in August 2021 and is ongoing. One patient is currently enrolled in the oral arm at Thomas Jefferson University in the USA. Safety is assessed according to the CTCAE v5. Tumor response in lymph nodes is determined per the RECIST 1.1 and in skin via clinical examination with serial tumor measurements. Key eligibility criteria include 1) diagnosis of RDEB and associated measurable, advanced cSCC confirmed histologically 2) failure to respond to standard of care including excision for localized disease 3) no concomitant cancer therapies. Clinical trial information: NCT04177498 .